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Topic: TI-83 and the normal approximation (fwd)
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Bob Hayden

Posts: 2,384
Registered: 12/6/04
TI-83 and the normal approximation (fwd)
Posted: Feb 6, 1997 9:28 AM
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----- Forwarded message from John Magee -----

Using the TI-83 normal approximation you would get .2248 from
normalcdf(-999,10,12.5,sd) with the continuity correction you would get .2727
from normalcdf(-999,10.5,12.5,sd). For those of you unfamiliar with TI-83
normalcdf(lowerbound, upperbound, mean, sd) returns area under curve quickly.

The student had done simply binompdf(100,0.125) stored to L1 and then did
sum(L1,1,11) and arrived with .280999. TI-83 binompdf(100,0.125) returns
all probabilities from 0 to 100 for p = 1/8. He summed items 1 to 11 to get
P(0) through P(10). He was, with ease at which he had done this, amazed
that anyone would do it the other way.

----- End of forwarded message from John Magee -----

I can't say anything about the TI-83, but all of these computational
shortcuts and approximations are relative to some particular computing
technology. For example, the "computational formula" for variance and
standard deviation harks back to mechanical desktop calculators. The
methods seem to take on a life of their own and continue to be used
long after there is any need for them. One of the functions of youth
is to question this!-)

| | Robert W. Hayden
| | Department of Mathematics
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| | Plymouth, New Hampshire 03264 USA
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